An additional and important advantage of the polyethylene composition of the present disclosure is that it can be melt-processed at unusually high shear rate values, which mean high processing speeds and/or reduced melt-processing temperatures, without encountering flow-instabilities that generally produce unacceptable defects in the resulting formed articles (e.g. shark skin or melt-fracture aspects), even in the absence of processing aids.
Moreover, the fast crystallization kinetics of the present composition, which provides a critical contribution to its superior processability, also provides an unusually reduced shrinkage in the resulting formed articles, thus allowing for a remarkable dimensional stability.
The composition of the present disclosure provides an unmatched balance of mechanical properties and processability with respect to many known polyethylene compositions for the same use, as disclosed in U.S. Pat. No. 6,201,078.
In this regard, the polymers disclosed in U.S. Pat. No. 6,201,078 achieve a relatively low balance of swell ratio and environmental stress cracking resistance, as shown in the examples therein.
The problems associated with high impact resistance, reducing the flow-instabilities and improving the dimensional stability (lowering shrinkage) are not overcome in the above referenced patent.